AU730538B2 - High accuracy automatically controlled variable linear seed spacing planting apparatus - Google Patents

Description

P/00/01 1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT a 4* 9.

a a Invention Title: High accuracy automatically controlled variable linear seed spacing planting apparatus The following statement is a full description of this invention, including the best method of performing it known to me/us: FFIPMELC6991 06003.3 WO 96/25704 W96/257 PCTUS96/01880

DESCRIPTION

HIGH ACCURACY, AUTOMATICALLY CONTROLLED VARIABLE LINEAR SEED SPACING PLANTING APPARATUS BACKGROUND OF THE INVENTION SThis invention relates generally to a planting apparatus, and more particularly to a planting apparatus wherein the preselected linear seed or plant spacing in the growing medium (hereinafter the "field") is adjustable while the planting apparatus is in motion, and is accurately determined and delivered to the field irrespective of any wheel slippage or sliding by the planting apparatus that ordinarily occurs in planting operations.

Farming is a highly labor intensive and cost driven activity, and the farming industry is 15 constantly striving to decrease farm labor, decrease relicid farm costs, and increase farm yields (often measured on a yield per area, such as on a yield per acre basis). As a consequence, present day farming techniques employ, among other things, the automated planting or transplanting (collectively "planting") of crops.

Present day automated planting is ordinarily accomplished by having a moving vehicle (hereinafter WO 96/25704 PCTIUS96/01880 2 "tractor") pull a planting apparatus having one or more seed or plant dispensing devices (collectively "seed dispensers") across a field. The seed dispensers are often arranged in one or more rows on the frame of the planting apparatus, and the rows on the frame are oriented transversely to the direction of travel by the tractor. The seed dispensers are ordinarily arranged at distances corresponding to the i width of furrows in the portion field to be planted by 10 the planting apparatus.

The rate at which seeds or plants (collectively "seeds") are dispensed by the seed dispensers is generally determined by a drive mechanism which operates a seed metering apparatus, such as a rotating seed dispensing disc, which has a discrete number of holes or pockets ("holes") which in turn dispense a discrete number of seeds per revolution of the drive mechanism or seed metering device. The drive mechanism, in turn, typically is rotatably connected to a free-rolling wheel, for example, via a power transmission system such as gears, chains and sprockets, or pulleys. The freerolling wheel is typically mounted on an axle connected to the frame of the planting apparatus on WO 96/25704 PCT7US96/01880 3 which the seed dispensers are mounted. Other means of directly or indirectly driving a seed metering device directly or indirectly off of a free-rolling wheel are known in the art as well, and will not be discussed herein in detail.

The rate at which seeds are dispensed may be and often is determined by manually adjusting the drive mechanism connection (such as a gear or chain and sprocket ratio adjustment), which in turn determines the rate of revolution of the drive mechanism, and, as a result, the seed dispensing disc, per revolution of the free-rolling wheel. By manually adjusting the drive mechanism connection, the operator can determine the number of seeds to be delivered per 15 linear distance travelled by the planting apparatus, assuming a substantially pure rolling motion absolutely no slippage -or sliding) by the free-rolling wheel of the planting apparatus.

In order to economically obtain the maximum crop yield per acre while minimizing costs from, for example, seed waste from planting more seeds than a.

particular portion of the field will have nutrients to support, the operator of the planting apparatus (hereinafter "farmer") must be able to accurately WO 96/25704 WPCT/US96/01880 4 control and accurately adjust (preferably while the planting apparatus is in motion) the number of seeds planted per linear distance of travel by the planting apparatus.

It has been determined that different portions of a field being planted by a farmer may vary widely in ability to supply nutrients to support a crop; a farmer's field may have a wide spectrum of high yield, medium yield, and low yield areas.

10 scattered throughout the acreage to be farmed.

Ideally, a farmer would like to accurately plant seeds closer together linearly in a high yield area, and farther apart linearly in a low yield area, and to be able to do so without stopping the planting apparatus 15 and, dismantling and readjusting the drive mechanism each time the planting apparatus travels from high to medium to low yield areas of a particular field. Because of the farmer's inability with many prior art planting devices to accurately vary linear seed spacing without the time-consuming and labor intensive practice of stopping and adjusting, e.g., the drive mechanism for the seed dispensers, farmers often set the linear plant spacing at a predetermined constant rate (sometimes referred to as an "average WO 96/25704 PCTIUS96/01880 rate") for the field. This practice resulted in (1) lower than optimum crop yield in high yield areas of the field due to underplanting, or overplanting (resulting in seed waste) in -low yield areas of the field, or both. These outcomes had adverse economic impacts on the farmer.

In order to optimize crop yield by accurately dispensing seeds at predetermined linear spacings, a farmer would prefer to be able .to accurately control the distance between seeds. For example, when planting corn, farmers may prefer the nominal linear distance between seeds in a medium yield portion of the field to be 8.0 inches, in high yield portions to be 6.0 inches, and in low yield portions to be 12.0 inches. The farmer might prefer a wide spectrum of other spacings to be available as well, depending upon, among other things, soil conditions. Consequently, a farmer would prefer to be able to accurately control nominal linear seed spacing within increments of 0.125 inches or less in such applications. The nominal spacing and increments may, of course, vary, depending upon, among other things, the crop.

WO 96/25704 PCT/US96/01880 6 Prior art automated planting apparatus in which the seed dispensing rate depended upon a drive mechanism coupled to a free-rolling wheel of the planting apparatus lacked the' ability to control linear seed spacing with the accuracy desired. This is due, in part, to the fact that in ordinary farming conditions the free-rolling wheel connected to the drive mechanism of the planting apparatus does not operate with a pure rolling motion, and unless the 10 free-rolling wheel connected to the drive mechanism purely rolls, seeds are dispensed at a rate that will not accurately and consistently achieve the desired spacing per linear distance travelled by the planting apparatus.

For example, in the crumbling topsoil typically encountered in many farming applications, the free-rolling wheel of the planting apparatus pulled by the tractor may slide intermittently and at unpredictable intervals. When the wheel slides instead of rolls, the rotating drive mechanism connected to the aforesaid wheel which operates the seed dispenser will not drive the seed dispenser (or will drive it at a slower rate than if it were purely rolling) which results in less seeds being dispensed CD/99096019.3 7 than desired per linear distance travelled by the planting apparatus. This is because the planting apparatus may travel forward despite the non-rotation of the free-rolling wheel as a result of the sliding mode of travel. Similarly, as the freerolling wheel encounters crumbling topsoil beneath it, the wheel may over-rotate, or slip although the wheel rotates, the planting apparatus does not move relative to the ground, similar to an automobile spinning its wheels in the snow), resulting in the seed dispenser dispensing seeds at a rate greater than that desired per linear distance travelled by the planting apparatus.

It is an object to at least in part to alleviate the abovementioned difficulties.

SUMMARY OF THE INVENTION °o In one aspect, the invention provides the combination of a low speed Doppler effect radar and a signal conditioning circuit, wherein said signal conditioning circuit further includes: eeo* 15 a phase-locked loop including a voltage controlled oscillator; an electronic circuit for preventing the operating frequency of the voltage controlled oscillator from migrating if a return signal from the Doppler effect radar intermittently fades or disappears.

In a further aspect, the invention further provides the combination of a low speed Doppler effect radar and a signal conditioning circuit, wherein a combined return signal as refined through said signal conditioning circuit is capable of accurately indicating the relative speed of the target at which the radar is directed to within 0.01 miles per hour or less.

Preferably, the combination is adapted for use with a planting apparatus, the speed of which relative to a field is preferably determined by a low R speed capability Doppler effect radar unit (hereinafter "low speed radar") 4 such as that manufactured by Entra Corporation, model number CD/9906019.3 8 LR100 (or other devices that similarly are capable of sensing vehicle speed or distance travelled relative to the ground, independent of wheel rotation) coupled with a signal conditioning circuit that filters out unwanted signals so as to provide a highly accurate low speed sensitive radar signal. The driving mechanism for the seed metering device of the seed dispensers is preferably a highly responsive proportionally controlled hydraulic motor circuit that is further controlled and monitored by a feedback mechanism via a programmable control circuit device.

*e In general terms, the rate of speed or distance travelled is accurately 10 determined by the low speed radar and signal conditioning circuit. Preferably, the rate or distance is fed into a programmable control circuit (hereinafter "microprocessor") together with the desired linear seed spacing as selected by the farmer and as ordinarily input by the farmer through an input mechanism such as a display unit located remotely from the planting apparatus, for example, in the vicinity of the cab of the tractor. Those inputs are used by the microprocessor to determine (despite the changing ground speed of the planting apparatus) the desired rate of flow of hydraulic fluid to the hydraulic motor (which, in turn, determines the desired hydraulic motor speed) which, in turn, operates the.seed metering devices in the seed dispensers at the appropriate rate so as to dispense 20 seeds at highly precise and consistent intervals heretofore unattainable in prior art devices, all independent of any sliding and slippage that the wheels of the planting apparatus or tractor encounter in the field.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a tractor coupled to the planting apparatus, including a partial cutaway view of a planting apparatus.

Fig. 2 is a top view of a tractor coupled to the planting apparatus.

UVI~~YIVV I U i 9 Fig. 3 is an exploded view of a portion of the planting apparatus, including the hydraulic motor, an active speed sensor, a single transmission, and a single seed dispenser, including a partial cutaway view of the seed dispenser.

Fig. 4 is a block diagram of the major electrical components of the planting apparatus, illustrating their electrical communication with each other and with the hydraulic safety valve and hydraulic proportional valve, including a partial schematic view of the hydraulic circuit.

Fig. 5 is a schematic diagram of the hydraulic motor circuit, including the 10 electrical communication between elements of the hydraulic motor circuit and the S• microprocessor.

oS Fig. 6 is a front view of the display unit.

4 Figs. 7A 7C are schematic diagrams of the electrical components of the display unit.

Figs. 8A 8E are schematic diagrams of the electrical components of the omicroprocessor circuit.

.Fig. 9 is a schematic diagram of the electrical components of a radar preamp.

.Fig. 10 is a schematic diagram of the electrical components of a signal conditioning circuit.

Fig. 11 is a schematic diagram of the electrical components, isolating those components most directly associated with the microprocessor, and illustrating electrical communications between the microprocessor and other electrical components with which it communicates.

Fig. 12 is a schematic diagram of the electrical components for the input and output circuits between the microprocessor and other electrical/mechanical components with which it communicates.

Fig. 13 is a block diagram illustrating the electrical systems in the described embodiment, and the electrical communications between those electrical systems.

Fig. 14 is a flow chart schematic for the microprocessor, illustrating generally the logic of the computer code executed by the microprocessor.

Fig. 15 is a functional block diagram schematic of the signal conditioning 10 circuit.

o* Fig. 16 is a flow chart schematic of the computer logic for background O:V: functions accessed by the main program of the microprocessor via interrupts.

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•5So ooS o oS CUIS9OSGO1 9.3 Pages 1110 14 are intentionally blank a a.

*a a a WO 96/25704 PCT/US96/01880 15 DETAILED DESCRIPTION OF THE ILLUSTRATED

EMBODIMENTS

Referring generally throughout to the Figures, and specifically here to Figs. 1, 2, and 3, the planting apparatus 24 includes one or more seed dispensers 2 that are located on a frame 4 which, in turn, is typically mounted on free-rolling wheels 6, but can be mounted on any other known means of transporting such frames, for example, on skids (not illustrated). The frame is ordinarily pulled or 10 pushed by a vehicle, typically pulled by a tractor 8.

The seed dispensers may be of various known constructions and need not be described in detail.

Those skilled in the art will recognize that various seed dispensers may be used in conjunction with the invention without departing from the teachings of the invention.

One common seed dispenser design.includes a seed hopper 10, and includes seed metering devices 12 capable of dispensing seeds intermittently. For example, a seed metering device 12 may be a typical device wherein a plurality of seeds 18 are gravity-fed or vacuum-fed into a rotating disc 14 with one or more evenly-spaced holes 16, which are larger than the seed 18 to be planted and which are capable of capturing WO 96/25704 PCTIUS96/01880 16 gravity-fed or vacuum-fed seeds 18, which are then released to the field below when the rotating disc rotates to a position wherein the hole 16 in the disc 14 holding an individual seed 18 aligns itself with the release point 20 above the seed chute 21 of the seed dispenser 2. Thus, it will be recognized that the rate at which seeds are dispensed to the ground below in this exemplary seed dispenser can be adjusted by regulating among other things, the number of holes o 10 in the rotating disc 14, or the rotational speed of the disc in the seed metering device 12, or both.

Seed monitoring devices or seed counting devices of known cohstruction (not illustrated) may be included in the seed dispensers to detect, for example, jamming 15 of or other malfunctions of the seed dispensers, or to further monitor seed dispensing.

Referring to Figs. 2, 3, 4, in the described example of one embodiment of the invention, the operating rate of the seed metering devices of the seed dispensers, the speed of rotation of the discs, may be regulated by.a proportionally controlled hydraulic motor 42. While other proportionally controlled motors operable at the direction a microprocessor 60 may be used, the inventors have WO 96/25704 PCTIUS96/01880 17 determined at this time that the relative simplicity, reliability, and quick reaction or response time of a proportionally controlled hydraulic motor 42 having a fast-reacting and accurately controlled hydraulic proportional valve 44 make such a motor and hydraulic motor circuit 40 a desirable choice. In the described embodiment, the hydraulic motor may be a motor such as the R-series motor manufactured by the Char-Lyn division of Eaton Corporation.

0S 10 A proportionally controlled hydraulic motor circuit 40 useful in carrying out the invention is described below. A hydraulic motor 42 is connected "0 directly or indirectly via gears, chain and

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sprockets, pulleys, or other known power transmission linkages) to the seed metering devices 12 via, for ee*' example, a rotatable shaft 22, with the linear rate of dispensing the seeds 18 per unit of distance travelled being a function, in part, of the speed of rotation of the shaft 22 and the number of holes 16 in the rotating discs 14. The rotational speed of the shaft 22 is, in turn, a function of the rotational speed of the hydraulic motor 42. In the illustrated embodiment, the rotational motion of the hydraulic motor 42 is transmitted to the rotatable shaft 22 WO 96/25704 PCT/US96/01880 18 through a transmission device 23 including a series of shafts 29, sprockets 25, and chains 27 in a manner known to those skilled in the art such that rotation of the hydraulic motor 42 will cause a corresponding rotation at a determinate rate in the rotatable shaft 22 and the rotating disc 14.

f- The hydraulic motor 42 is connected hydraulically to a fast-reacting and accurately controlled hydraulic proportional valve 44, for example, a hydraulic proportional valve such as the valve sold by Fluid Power Industries as model number 8352105, or as described in United States Patent No.

4,121,610. Such a hydraulic proportional valve 44 is capable of adjusting the rate oft, flow of hydraulic 15 fluid therethrough very quickly (on the order of 0.150 seconds, or less) in response to an electrical signal; the proportional valve 44 will quickly adjust toallow more or less hydraulic fluid to pass through to the hydraulic motor in response to an electrical signal. The electrical signal input to the proportional hydraulic valve is received from the microprocessor 60, through electrical lines 61, as will be discussed further herein.

WO 96/25704 PCT/US96/01880 19 A quantity of hydraulic fluid is supplied to the hydraulic proportional valve 44 via a supply circuit 56. The hydraulic proportional valve 44 determines, depending on the electrical signal S arriving from the microprocessor 60 via electrical lines 61 (which proportionally opens or closes the hydraulic proportional valve 44), the amount of hydraulic fluid that will pass therethrough via the operating circuit 58 to- the hydraulic motor 42. The rotational speed at which the hydraulic motor 42 operates (which, in turn, helps to determine the rate of dispensing seed) is a function of the amount of flow of hydraulic fluid through the hydraulic motor 42, as determined by the proportional valve 44. After hydraulic fluid passes through the hydraulic motor 42, the hydraulic fluid in the described embodiment flows through -a return circuit 52, and may pass to a reservoir 46. Similarly, hydraulic fluid that is not allowed to pass through the proportional valve 44 to the hydraulic motor 42 may be diverted through a diversion circuit 54 to the return circuit 52, and may pass to the reservoir 46. A hydraulic pump 48 is connected hydraulically to pump hydraulic fluid between the reservoir 46 and the proportional valve WO 96/25704 PCTIUS96/01880 20 44, and may be connected between the reservoir 46 and the supply circuit 56 via a replenishing circuit 59, pumping hydraulic fluid at a relatively constant rate in the described embodiment.

In addition to the hydraulic proportional valve 44, a safety valve 45 may be interposed in .the hydraulic circuit between the hydraulic proportional valve 44 and the hydraulic pump 48. The safety valve .i 45 can take the form of a two-position, three way valve such as that manufactured by Fluid Power Industries as model number MV4-24-12VDC. The placement of the safety valve 45 is such that if the planting apparatus 24 is not in motion as determined by the ground speed sensor 26 and the signal conditioning circuit 102 via the microprocessor the microprocessor 60 sends a signal to cause the -safety valve 45 to divert the hydraulic fluid through a diversion circuit 54 the hydraulic motor circuit 40 is closed); if, on the other hand, the planting apparatus 24 is in motion, the microprocessor sends a signal to cause the safety valve 45 to

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direct the hydraulic fluid through open) the supply circuit 56. Those skilled in the art will recognize that the safety valve 45 may be omitted, or WO 96/25704 PCTIUS96/01880 may be combined with the proportional valve 44 into a single valve without departing from the teachings of the invention.

Referring to Figs. 1 and 2, a highlyaccurate ground speed sensor 26 coupled with a signal conditioning circuit 102 (Figs. 8, 9, and 10) capable of determining the speed of or distance travelled by the planting apparatus 24 relative to the field to be planted and independent of the rotation of the wheels 6 of the planting apparatus 24 (or the wheels 28 of S: the tractor 8) is connected to the planting apparatus 24 or the tractor 8. In the embodiment illustrated, the ground speed sensor 26 is connected to the planting apparatus 24. As previously noted, the 15 described embodiment of the invention utilizes as a ground speed sensor 26 a low speed radar capable of operating over the preferred operating speed of a planting apparatus 24 between 0.10 and 12.0 miles per hour and when coupled with a signal conditioning circuit 102 through a radar preamp 101, is capable of determining relative ground speed with high accuracy (preferably within at least 0.01 mph). The ground speed sensor 26 provides periodic input concerning the relative ground speed of WO 96/2704 PCT/US96/01880 22 or distance travelled by the planting apparatus 24 on an ongoing basis by communicating, preferably electronically, with the microprocessor 60, via the circuitry referenced above: Referring to Figs. 1, 2, and 6, the described embodiment of the invention also utilizes an input device, such as the display unit 62 shown in the illustrated.embodiment, which permits the farmer, for example, to use plant spacing inputs 66 to select (or 10 to change) a desired linear seed spacing of the dispensed seeds 18. The plant spacing selected may be shown on plant spacing display 68. The display unit 62 may also allow the farmer to input other information, such as the number of seeds dispensed per 15 rotation of each individual rotating disc 14 (ordinarily the number of holes 16 in the disc 14) by using disc capacity inputs 70. The disc capacity selected may be shown on disc capacity display 72.

The inputs may take the form of electronic switches known in the art, and the displays may take the form of LED's, LCD's or other display means known in the art, and will not be discussed in detail here. The circuitry of the display unit for the described embodiment is shown schematically in Fig. 7; however, WO 96/25704 PCTUS96/01880 23 =hose skilled in the art will recognize that an input or display unit using circuitry different from that described and illustrated herein could be utilized without departing from the -teachings of the invention.

Referring again to Figs. 1, 2, and 6, the display unit 62, in turn, communicates this information, preferably electronically, to the microprocessor 60 via electrical lines 61. .The display unit 62 may also include monitors to ensure correct operation of the planting apparatus, such as monitors to detect seed jams or other malfunctions in the seed dispensers (not illustrated), or operational speed alarms 64 capable of monitoring the ground speed of, the tractor as operated by the farmer to 15 ensure that it is within the appropriate operational range of the planting apparatus 24, etc.

Referring to Figs. 2, 3, and 4, operationally engaged with (and, in the illustrated embodiment, adjacent to) the hydraulic motor 42 in the described embodiment is an active speed sensor which in turn communicates, preferably electronically, with the microprocessor 60 as well. In the illustrated embodiment, the active speed sensor senses the rotational speed of the shaft 29 connected WO 96/25704 PCTJUS96/01880 24 to the hydraulic motor 42 (which in turn determines, in part, the seed dispensing rate of the seed metering devices); however, it will be recognized in the art that the active speed sensor may be used to sense the rotational speed of other components directly or indirectly engaged with the hydraulic motor 42, for example, the shaft 22 or the rotating disc 14. One embodiment of an active speed sensor 50 known in the art and useful in carrying out the invention is a so- 10 called Hall effect sensor wherein one or more magnets in the shaft 29 create a magnetic flux that results in an electrical pulse as the magnet rotates past the active speed sensor 50 the Hall effect sensor)

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although other appropriate active speed sensors such as transducers may be used as well.

The active speed sensor 50 sends a signal to the microprocessor 60 which allows the microprocessor to determine whether the disc 14 is dispensing seeds 18 at the appropriate rate determined by the microprocessor to achieve proper linear seed spacing at the then-current operational speed of the planting apparatus 24 as determined via the ground speed sensor 26. If the microprocessor 60 determines that the rate of dispensing seeds 18 detected by the active speed WO 96/25704 PCT/US96/01880 25 sensor 50 is too fast that the seeds are being dispensed too closely), then the microprocessor adjusts the flow of hydraulic fluid by sending an electronic signal proportionally closing the hydraulic proportional valve 44, thus slowing the hydraulic motor 42, the rotating shaft 22, rotating disc 14, and

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ultimately the seed dispensing rate. The converse would, of course, be true where the seed dispensing rate detected by the active speed sensor 50 is S* 10 determined to be faster than appropriate.

The microprocessor 60 may take the form of microprocessors currently available from a number of manufacturers, such as the Motorola model no.

MC68HC11EFN and serves to calculate the appropriate 15 electrical signal to be provided to the hydraulic proportional valve 44 (and safety valve 45), which, in turn, determines the rate of hydraulic fluid passing through to the hydraulic motor 42, which in turn controls the rate of operation of the seed metering devices 12, which thereupon controls the linear spacing at which seeds 18 are dispensed to the field by the planting apparatus 24.

Because the microprocessor quickly and accurately correlates the rate at which seeds 18 are WO 96/25704 PCTfUS96/01880 26 dispensed by the seed metering devices 12 to the ground, as well as the ground speed or distance travelled of the planting apparatus 24 as determined by the ground speed sensor 26 through the radar preamp 101 and the signal conditioning circuit 102, ground speed is determined independent of wheel rotation, with the inherent slippage and sliding), the seeds are accurately and consistently dispensed at the Spredetermined plant spacing set by the farmer, and may 10 be changed by the farmer "on the fly" via the display unit 62.

The microprocessor takes the selected linear 'spacing of the seeds that the farmer preselects (or changes) and inputs this information through the display unit 62, and using the relative ground speed or distance travelled of the planting apparatus 24 as an input from the ground speed sensor 26 through the radar pre-amp 101 and the signal conditioning circuit 102, calculates the appropriate rate at which the hydraulic motor 42 should operate to cause the seed metering devices 12 to dispense seeds 18 at the desired intervals. A signal is then sent by the microprocessor 60 to the hydraulic proportional valve 44 to increase, decrease, or maintain the flow of WO 96/25704 PCTUS96/01880 27 hydraulic fluid therethrough in order to achieve the appropriate hydraulic motor speed.

The active speed sensor 50 operationally engaged with the hydraulic motor 42 ensures- further accuracy and more responsive control by providing input to the microprocessor 60 as to whether the.

hydraulic motor 42 is in fact operating at the rate.

determined by the microprocessor; if it is not, the microprocessor 60 calculates the differential and sends a signal to the hydraulic proportional valve 44 to further increase or decrease the flow of hydraulic fluid, which in turn further refines the operating speed of the hydraulic motor 42 and the resultant seed dispensing rate and linear seed spacing.

As noted above, the ground speed sensor 26 provides a signal that is filtered via a signal conditioning- circuit 102 (Fig. 10) after passing through the radar pre-amp 101 (Fig. The radar pre-amp 101 is a pre-amp circuit such as that shown in Fig. 9. As will be recognized by those skilled in the art, other pre-amp circuits could be substituted for the circuit shown in Fig. 9 without departing from the teachings of the invention.

WO 96/25704 PCTUS96/01880 28 A signal conditioning circuit 102, such as that shown in Fig. 10, is desirable to determine the ground speed or distance travelled with sufficient accuracy to achieve the goal of achieving accurate plant spacing over the operable range of planting apparatus 24, for example, in the described embodiment, over a range of plant spacings between 1 inch to 24 inches in 1/8 inch increments. Given that -a typical K band radar antenna useful in low speed 10 Doppler radars returns a substantially accurate signal frequency in the range near 72 Hz (per mile per hour of the moving vehicle), that means that at 0.1 mph, the low end of the described embodiment of the operational speed of the planting apparatus 24, the 15 period of the signal would be 7.2 Hz. For a radar unit to sample 10 waveforms under such circumstances would take 1.4 seconds. Because it would- be preferable to sample more than 10 waveforms to obtain .a statistically significant sample and achieve the accuracy and reliability desirable for the invention to carry out accurate seed planting, and because doing such sampling would result in separate samples being taken at intervals too infrequent to accurately control the rotational speed of the hydraulic motor, WO 96/25704 PCT/US96/01 8 8 0 29 the signal conditioning circuit 102 such as that shown in Fig. 10 is desirable.

Moreover, the signal conditioning circuit 102 also aids in processing the radar sigrral to eliminate extraneous signal noise. For example, when Sthe ground speed sensor 26 in the form of a low speed Doppler effect radar is mounted on a slow moving vehicle and pointed toward the ground, the return signal may be a composite signal that appears to be of constantly changing magnitude and symmetry, and which :may result in periods of nearly complete signal cancellation, resulting intermittently in a return signal that may be loaded with extraneous signals unrelated to the ground speed 'or distance travelled.

The desired return signal consists of multiple images of the same frequency which do relate to the speed of the vehicle, and hence, the distance travelled, even though such signals too vary in phase and magnitude.

Those return signals truly related to the ground speed or distance travelled are selected by the signal conditioning circuit 102, as opposed to those signals unrelated to ground speed, with the signal conditioning circuit 102 adjusting for those occasions WO 96/25704 PCT/US96/01880 30 where the return signal fades or drops out altogether at intermittent intervals.

Prior to this invention, attempts to deal with the problems described-above with low speed Doppler effect radar signals have involved the use of tracking filters or phase-locked loop circuits. While tracking filters may eliminate signals that are significantly out-of-band, they are less effective in o dealing with the very low frequencies that would be 10 associated with radars mounted on agricultural equipment, and are largely ineffective in reducing measurement uncertainty.

Phase-locked loops ("PLLs") are known in the art, and need not be described in detail here; PLLs 15 typically utilize a Voltage Controlled Oscillator a frequency/phase detector for generating an error or control signal, and a VCO control filter arranged in a closed-loop system. Such systems operate as frequency filters and may operate at very low frequencies; however, typical PLL implementations have a property that is very undesirable in connection with the invention. In the absence of a significant return signal, when a return signal from the radar intermittently fades, decreases in strength, or WO 96/25704 PCT/US96/01880 31 disappears, the PLL will migrate to the VCO center frequency or to the VCO's lowest operating frequency, and will transmit a signal accordingly. Thereafter, each time the radar return signal reappears, the PLL attempts to acquire a "lock" on that return signal, and this sometimes requires several signal periods.

p.- Frequently, the signal will fade or disappear again before the PLL can adequately lock on the signal.

This results in the signal in the PLL migrating to varying degrees intermittently between the VCO o frequency, which is not related to ground speed or distance travelled, and the return signal frequency; in the context of the invention, this would result in inaccurate rotational speed modulation for the 15 rotating discs 14 in the seed metering devices 12. In other words, the rotational speed of the rotating discs 14 would migrate intermittently as well due to the PLL's signal migration, resulting in inaccurate linear plant spacing.

20 The signal conditioning circuit 102, shown in detail in Fig. 10 and in functional block diagram form in Fig. 15, provides a unique circuit arrangement within a PLL circuit such that the radar return signal only influences the VCO while the return signal is WO 96/25704 PCT/US96/01880 32 adequate in magnitude; when the return signal is inadequate when it intermittently fades or disappears), the PLL remains at its last locked frequency it does not migrate) until-adequate return signal strength is again detected.

The output from the signal conditioning circuit 102 thus constitutes a much more stable image with only minor corrections occurring at any given instant. A secondary output signal from this signal conditioning circuit varies in duration relative to .i the period (duty cycle) with the magnitude of the radar signal and is used as a signal quality indication. The stable output signals from the signal conditioning circuit, the inventors have found, 15 permits the measurement of ground speed between at least 0.10 and 12.0 mph, with an accuracy of plus or minus 0.01 mph, therefore permitting accurate calibration of seed placement to within 0.125 inches or less in connection with the invention described 20 herein.

Referring to Figs. 8, 9, 10, 13 and 15, the return signal from the ground speed sensor 26 (the Doppler effect radar in the described embodiment) via the radar pre-amp 101 passes through the signal WO 96/25704 PCTIUS96/01880 33 conditioning circuit 102, which includes a signal squaring circuit that ignores or effectively filters low level noise signals and presents a clear square wave to the phase detector. The return signal is also directed through two signal magnitude threshold comparators, with the outputs combined to gate the phase detector output to the loop filter when the absolute value of the return signal is above a predetermined level. The loop filter then controls the VCO frequency so that.it will consistently be the average value of the return signal, which has been validated through the foregoing signal conditioning procedure.

The combined output of the signal magnitude threshold comparators varies in duration relative to the period (duty cycle) with the magnitude of the return signal, which is used by the microprocessor as a signal quality indicator.

The output signal of the signal conditioning 20 circuit may be treated as a ground speed measurement, and integrated by one or more known means to determine distance travelled; however, the inventors have found it advantageous to treat the output signal as a progressive position measurement. For example, where WO 96/25704 PCTIUS96/01880 34 the period of a radar signal is approximately 72 Hz (actually, a return signal of 71.9486 Hz) per mile per hour of the moving vehicle, that equates to a distance travelled of approximately 0.24462 inches per return signal cycle. mile/hour) x (1 hour/3600 seconds) x (5280 feet/1 mile) x (12 inches/I foot) x (1 second/71.9486 cycles) 0.24462 inches/cycle). By accumulating radar return signal pulses, the distance travelled can be determined by direct proportionality.

Similarly, the rotational speed of, the rotating discs 14 as determined by the active speed sensor can be determined in terms of rotational speed; however, the inventors have found it advantageous to treat that signal as a mechani.sm position signal.

15 Because the pulses of the active speed sensor 50 may be recognized on both the rising and falling portions of the pulse, the frequency with which the active speed sensor 50 provides position information is effectively doubled.

20 Referring to Figs. 3, 4, 5, 6, 14, and 16, microprocessor 60 uses the signals obtained from the signal conditioning circuit 102 and from the active speed sensor 50 in order to regulate the speed of the hydraulic motor 42 such that the seeds 18 are WO 96/25704 PCTIUS96/0 1880 35 dispensed at the desired spacing as input through the plant spacing inputs 62. It will be recognized that for a desired seed spacing, and for a given number of holes 16 in the rotating discs 14, there exists a mathematical relationship between the pulses of the return signal from the ground speed sensor 26 and the pulses from the active speed sensor 50, and the number (or fraction of the number) of seeds 18 dispensed.

The microprocessor 60 accumulates the pulses of the return signal of ground speed sensor 26 for the signal o \o\o conditioning circuit 102 and compares the pulses of the active speed sensor 50 (based upon the plant :spacing input), and to the extent that the rotational speed of the rotating disc is not appropriate to 15 achieve the desired plant spacing at the then-current operational ground speed of the planting apparatus 24, the microprocessor 60 corrects the speed of the hydraulic motor 42 by sending a signal to adjust the hydraulic proportional valve 44 accordingly, as 20 previously described.

For a given sampling period, the mathematical relationship between the signal received via the ground speed sensor 26 and the active speed sensor 50 utilized to correct the rotational speed of WO 96/25704 WO 9625704 PCT/US96/01880 36 the hydraulic motor 42 by proportionally opening or closing the hydraulic proportional valve 44 may be expressed generally as follows: (Number Of Target Radar Return Pulses)/(Number Of Target Active Speed Sensor Pulses)=((Desired Seed Spacing (in.))/(0.22462 in. per pulse))x((Number Of Holes In Rotating Disc)/(Number Of Pulses Generated Per Revolution Of The Rotating Disc)). (The 0.22462 inch figure used in connection with the described embodiment of the 10 invention represents the period of a 71.9486 Hz signal, the return signal for the radar per mile per hour travelled. Those skilled in the art will recognize that, for different embodiments of the invention, for example, using a different effective 15 return signal, this figure might have to be adjusted without departing from the teachings of the invention.) Thus, for any given setting for the planting apparatus 24, and for a desired seed spacing selected :*oe 20 by the farmer, the ratio between the Number Of Target Radar Return Pulses to the Number Of Target Active Speed Sensor Pulses Generated Per Revolution Of The Rotating Disc can be seen to be a constant For example, if the planting apparatus is set up to WO 96/25704 PCTIUS96/01880 37 generate 190 pulses per revolution of the shaft 29 (and, consequently, the disc 14), and assuming that there are 6 holes 16 in the disc 14, and assuming that the farmer desires to plant-at 6 inch spacing, the ratio between the Number Of Target Radar Return Pulses to the Number Of Target Active Speed Sensor Pulses r Generated Per Revolution Of The Rotating Disc or KT would be equal to in. per plant)/(0.22462 in. per pulse))x((6 holes (plants) per revolution)/(190 pulses per revolution))= 0.84353. This constant is recalculated by the microprocessor 60 whenever the planting apparatus starts, or the desired seed spacing or the number of holes 16 in disc 14 is changed.

Each time that a pulse is generated as a 15 result of a return signal from the ground speed sensor 26, the constant K, is added into an internal register in the microprocessor 60. Each time a pulse is generated by the active speed sensor 50, a unity value is added into an internal register in the 20 microprocessor 60. These tasks are performed in the background of the main program of the microprocessor through the use of interrupts. In the described embodiment, each pass through the program loop (every 4.096 mS) the microprocessor 60 determines the WO 96/25704 PCTIUS96/01880 38 difference between the two registers (effectively, the target number of pulses minus the actual number of pulses), and multiplies that difference by a gain factor; it then outputs that product as the pulse width modulation duty cycle for the hydraulic proportional valve 44. The task of controlling the toutput is also performed in the background of the main -program, using interrupts; The rotating speed of the hydraulic motor 42 and, hence, the shaft 29 and the disc 14, is adjusted by the microprocessor 60 in the above-described manner to generate a signal to the hydraulic proportional valve 44 so that the accumulated values in the two registers match.

The combined output of the signal magnitude 15 threshold comparators into the microprocessor 60 is caused to increment a register while the signal level is high. This task is performed in the background using interrupts. At intervals, the main program 0 acquires this value, clears the register for evaluation over the next interval, and divides it by the maximum possible register value. This result is used as a signal quality factor for validating the presence of the return signal from the ground speed sensor 26.

WO 96/25704 PCTIUS96/01880 39 In order that the planting apparatus 24 starts and stops planting seed coincident with the starting and stopping of movement of the planting apparatus 24, the microprocessor 60 senses: when the planting apparatus 24 has begun moving positively relative to the ground, and then sends signals opening Sthe safety valve 45 and/or the hydraulic proportional valve 44; when the planting apparatus 24 has ceased moving positively relatively to the ground, and then sends signals closing the safety valve 45 and/or the hydraulic proportional valve 44; and when no S: useable return signals are available from the radar for a prolonged.period of time, in which case the microprocessor 60 sends signals closing the safety 15 valve 45 and/or the hydraulic proportional valve 44.

When the microprocessor 60 sends a signal closing the safety valve 45 and/or the hydraulic proportional valve 44, it may also optionally send another signal, to the display unit 62 indicating that planting has stopped.

Referring to Figs. 11, 12, and 13 in the described embodiment, the microprocessor 60 signals the hydraulic proportional valve 44 by causing the output via the hydraulic proportional valve output CD/99096019.3 circuit 104 to be a PWM signal with a frequency of around 1 Khz and the duty cycle varied as required. The output circuitry for the hydraulic proportional valve 44 and the safety valve 45 (circuits 104 and 103, respectively), are similar, except that the hydraulic proportional valve output circuit 104 includes a current sensing shunt resistor in order to permit the microprocessor 60 to monitor the valve current. Both output circuits utilize N-channel Field Effect Transistors ("FETs") for low-side switching of the valves. The active speed sensor input circuit 105 utilizes a hysteresis comparator to square up the signal and reduce the effect of electrical noise. Those skilled in the art will recognize that input/output circuits other than those specifically illustrated and discussed herein can be utilized without departing from the teachings of the invention.

For purposes of describing a specific embodiment of the invention, an S00 exemplary program for the microprocessor 60 is found within the text of Australian 15 patent application 50229/96 (granted as serial number AU 703938) at pages 41 to 97, reproduced as a source statement, including comments as appropriate.

:i0 Many other objects, features and advantages of the invention will be more 0. fully realized and understood from the foregoing detailed description when taken in conjunction with the accompanying drawings wherein like reference numerals 20 throughout the various drawings are intended to designate similar elements and components.

It will be understood that the term "comprises" or its grammatical variants as used herein is equivalent to the term "includes" and is not to be taken as excluding the presence of other elements or features.